It was during the first half against Germany that Messi doubled over and vomited on the pitch.
Despite several medical tests, Argentina and Barcelona team doctors haven't been able to find the cause of Messi's problem.
The striker has played it down, saying it's just something that happens to him in training, during matches and even when he's at home.
It doesn't appear to affect his performance, though. Messi has gone on to score in several matches after throwing up on the pitch.